can否定形式有两种：can"t或 can not。过去式 could有couldn’t和could not。

can：modal能，会;(表示知道如何做)懂得;与动词feel、hear、see、smell、taste 连用；

n.金属罐;一听(的量);金属容器，塑料容器；

v.把(食品)装罐保存

扩展资料

How long can a human being go without sleep?

人不睡觉能活多久？

Events could have developed in a dramatically different way.

事情本来可以发展成另一种样子。

You can't stop people from saying what they think.

人们怎么想就会怎么说，你阻止不了。

You could see from his face that he was lying.

从他的表情上你可以看出他在说假话。